Simplify the magic required to create IPC message headers a bit.

chrome/browser/importer/firefox_importer_unittest_messages_internal.h

Index: chrome/browser/importer/firefox_importer_unittest_messages_internal.h
===================================================================
--- chrome/browser/importer/firefox_importer_unittest_messages_internal.h	(revision 68536)
+++ chrome/browser/importer/firefox_importer_unittest_messages_internal.h	(working copy)
@@ -2,15 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// This header is meant to be included in multiple passes, hence no traditional
-// header guard.
-// See ipc_message_macros.h for explanation of the macros and passes.
-
 #include "ipc/ipc_message_macros.h"
 
+#define IPC_MESSAGE_START FirefoxImporterUnittestMsgStart
+
 // Messages definitions for messages sent between the unit test binary and
 // a child process by FFUnitTestDecryptorProxy.
-IPC_BEGIN_MESSAGES(Test)
 
 // Server->Child: Initialize the decrytor with the following paramters.
 IPC_MESSAGE_CONTROL2(Msg_Decryptor_Init,
@@ -29,5 +26,3 @@
 
 // Server->Child: Die.
 IPC_MESSAGE_CONTROL0(Msg_Decryptor_Quit)
-
-IPC_END_MESSAGES(Test)